More available arguments for ycmcompleter-subcommands

[Shuangcheng-Ni]

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Why this change is necessary and useful

This change provides more available arguments for commands like YcmCompleter. The new available arguments --line_num= and --column_num= enables the commands to be executed at any position. Without these two arguments, the commands can only be executed at cursor position.

The result of the command YcmCompleter GetDoc --line_num=6 --column_num=2:

---

This change is 

[puremourning]

Thanks for making a PR!

Whats the practical use case for this?

can you add tests? And docs?

[codecov]

Codecov Report

Merging #4105 (b11ebef) into master (88efc6f) will decrease coverage by 0.10%.
The diff coverage is 33.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4105      +/-   ##
==========================================
- Coverage   86.41%   86.31%   -0.11%     
==========================================
  Files          33       33              
  Lines        4358     4361       +3     
==========================================
- Hits         3766     3764       -2     
- Misses        592      597       +5     

[Shuangcheng-Ni]

Thanks for making a PR!

Whats the practical use case for this?

can you add tests? And docs?

Thanks for your quick reply! You may take a look at my latest PR. I'm going to use commands like YcmCompleter GetDoc --line_num=v:beval_lnum --column_num=v:beval_col to get the document of the symbols at the mouse pointer.