Add user options and commands to customize wrap width value

[pomeh]

By default, Wrap Plus use Sublime Text settings wrap_width or rulers to know at which column to wrap text.

In some cases, it might be useful to define a custom width to wrap a specific file. I've added some options to do that:

• WrapPlus.wrap_width: a int to define the wrap width size, instead of using values from wrap_width and rulers, eq: "WrapPlus.wrap_width": 80,
• WrapPlus.wrap_width_custom_list: a list of predefined width size, to quickly switch to one of them using Command Palette, eg: "WrapPlus.wrap_width_custom_list": ["72", "80", "100", "120"]

I've also added a Command Palette entry which can be used in 3 different ways:

• very quickly change the current wrap width size to a fixed one, eq:

"command": "wrapplus_setwidth", "args": {"width": "72"}

• change the current wrap width size to one of the predefined width from WrapPlus.wrap_width_custom_list setting:

"command": "wrapplus_setwidth", "args": {"source_list": "wrap_width_custom_list"}

• change the current wrap width size to one of the rulers setting:

"command": "wrapplus_setwidth", "args": {"source_list": "rulers"}

All those command can be placed in all Sublime Text file (*.sublime-commands, *.sublime-keymap, *.sublime-menu)

[pomeh]

Almost one year and still no response. Can you merge this PR if you like it or close it if you don't @ehuss ?