Add rudimentary Synclude plugin.

Add:
	vim/scripts/Synclude/, vim/bundle/Synclude
		-Add Synclude plugin directory, and a symlink from `bundle/`.

	vim/scripts/Synclude/plugin/Synclude.vim
		-Add rudimentary, functional implementation of Synclude.

	vim/scripts/Synclude/groups.syn
		-Add groups file with a placeholder entry.
Refine Synclude.vim.

Add:
	vim/scripts/Synclude/plugin/Synclude.vim
		-Add configurable syntax-matches file path.
		-Rename global variables such that they include "synclude".
		-Add `SyncludeEdit`.

	vimrc, vim/scripts/Synclude/groups.syn -> vim/matches.syn
		-Specify custom syntax-matches file.
Add Synclude ftdetect, ftplugin.

Add:
	scripts/Synclude/(ftdetect/Synclude, ftplugin/synclude).vim
		-Add Synclude `ftplugin` file, with syntax matches for the
		plugin's matches-file.
Populate matches.syn, add SyncludeIncludeMatch().

Add:
	vim/scripts/Synclude/plugin/Synclude.vim
		-Move logic from `Synclude` command to `SyncludeIncludeMatch()`,
		which additionally verifies whether a given match is defined,
		and `echom` a warning otherwise.

	matches.syn, vim/ftplugin/(c, python).vim
		-Populate `matches.syn` with syntax matches shared by `c.vim`
		and `python.vim`; replace their definitions in either of the
		latter two files with `Synclude`.
Merge branch 'feature/vim-syntax-groups' into develop

Add Synclude vim plugin.