Fix bug: "\" has to be escaped or it tries to escape the next char
Refactor code to support visual mode operations

- Move handling of mode-specific quirks to FireboltFind() function
- Handle inclusive field of the Seek function by setting a key in
  s:firebolt to a function to be called during RepeatFind.  Replaces
  FwdRepeat and OpRepeat.  Those functions let too much of the
  abstraction leak out, but a Repeat callback function with the same
  signature of the original RepeatFind function preserves much of that.
- Modify maps to pass in strings instead of 1/0 for the operator
Fix bug: '\' need to be escaped individually or Seek's pattern breaks
Move SeekRepeat() out to get rid of screen flicker problem
Change Seek mappings to not clash with vim-surround. Use gl.