[less mode] Remove fixed list of tags

It makes no sense.

Issue #1466
[vim keymap] Add actionArgs for command 'i' 'I'
[vim keymap] Remove stray plus character

Issue #1525
Allow mode spec objects to have mime types as name

Other properties will be added/overridden in the config object for the
mime type.
[clike mode] Fix interaction of dontAlignCalls and statementIndentUnit

Closes #1518
Don't crash when getMode is passed null
Merge branch 'master' of https://github.com/marijnh/CodeMirror