Update all asset-related API's to support asset symbol as parameter

[abitmore]

User Story
As an API user I want to use asset symbols directly for all APIs. Some APIs support asset symbols, e.g. get_ticker, but others don't support, e.g. get_market_history.

Additional Context (optional)
https://bitsharestalk.org/index.php?topic=26699.0

CORE TEAM TASK LIST

• Evaluate / Prioritize Feature Request
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[oxarbitrage]

to be done after #989

[oxarbitrage]

changes will be made at the following api calls.

in database_api:

• get_assets
• get_limit_orders
• get_call_orders
• get_settle_orders
• get_collateral_bids
• subscribe_to_market
• unsubscribe_from_market
• get_required_fees

in api:

• get_fill_order_history
• get_market_history
• get_asset_holders
• get_asset_holders_count
• get_grouped_limit_orders

cli wallet changes:

other impacts

• get_ticker, get_24_volume, etc are fine as they use lookup_asset_symbols with the base and quote string, it can be an ID or a name. no changed needed.
• test cases that use asset_id_type(), asset_id_type(1), etc as an argument of one of the modified calls will need to be casted to a string with the asset id on it.

[oxarbitrage]

Please check ee0a8ce for support asset symbol or name in get_limit_orders

Additionally, commit also do the following(please check carefully as the same changes will be added to to at least get_call_orders and get_settle_orders:

• current version of get_limit_orders accepting ids is moved to implementation for internal use.
• changed database api to new version, after converting the strings to ids with get_asset_from_string it will call internal impl version.
• limit was not checked in this call so added a check into database api call get_limit_orders with a max of 100(this will end up in 200 results by keeping the current behaviour).
• added reserve of the results to increase performance a bit with a size of limit*2 in both calls(internal and api).

[abitmore]

get_limit_orders with a max of 100

I think it may break bitshares-ui.

[oxarbitrage]

closed by #1272