[LINST] Remove '_date' only for Standard Format

[zaliqarosli]

Brief summary of changes

This PR fixes the removal of '_date' by only allowing it to happen for Standard Date formats.

Currently, all date elements (standard, basic, and month/year) in linst instruments have their field names redefined as the substring appearing before '_date'. For example, if a date element is called 'enrolment_date_v2', the instrument field name becomes enrolment. The issue with this is that on saving the instrument, the save function will try to update a field called 'enrolment' in the instrument table which does not exist.

Now, the reason why this functionality existed in the first place is because the Standard Date format requires a field name ending with '_date'. Linst Standard Date formats are created by calling the NDB_BVL_Instrument class addDateElement() function which auto appends '_date' to the date element name. In order to avoid '_date' appearing twice, the NDB_BVL_Instrument_LINST class removes '_date' from the element name before calling addDateElement().

Basic Date and Month/Year formats call the NDB_Page class addBasicDate() function and the NDB_BVL_Instrument class addMonthYear) function respectively, both of which do not seem to auto append '_date' to the field name.

In this PR, if a Standard Date format field name does not already end with '_date' , a LorisException is thrown.

Testing instructions (if applicable)

1. Add a Standard Date field to the $loris/project/instruments/bmi.linst. You can add to the end of the file:

date{@}completion_date{@}Date of completion{@}{@}{@}BasicDate

2. Add the date field to the bmi SQL table. You can run in mysql:

alter table bmi add column completion_date date DEFAULT NULL;

3. On main branch, fill out the date field and click 'Save Data' on the bmi instrument front-end for any candidate. You will get the 'Something went wrong.' page. Check your apache error log, and you should see errors

Column not found: 1054 Unknown column 'completion' in 'field list'
Update statement did not execute successfully

'Inspect' the HTML date element on the browser, and notice that the input name is 'completion' instead of 'completion_date'.
4. On this PR branch, repeat the above step and you will get no errors (except for maybe 'Error running scoring algorithm' which is a separate issue I think is unrelated to this PR)
5. On this PR branch still, modify the last line of the bmi.list file to be:

date{@}completion_date{@}Date of completion{@}{@}{@}

This now changes the date element from a Basic Date format to a Standard Date format. A standard date format date field requires a not_answered '_status' field so run in mysql:

alter table bmi add column completion_date_status enum('not_answered') default NULL;

6. Refresh the instrument page, fill out the date field and click 'Save Data' again. You will get no errors. Inspect the HTML date element, and notice that the field name is completion_date and not completion_date_date
7. After finishing testing, you can delete the columns you had added. Run in mysql:

alter table bmi drop column completion_date;
alter table bmi drop column completion_date_status;

[ridz1208]

@cmadjar @driusan @zaliqarosli

I just want to say that I will use this PR from now on as an example for what testing instructions look like !!!