Make :ViewSession compatible with console Vim (issue xolox#74)

See issue xolox#74 on GitHub:
  xolox#74

Merge pull request xolox#70: Allow to turn off Sessions menu

See pull request xolox#70 on GitHub:
  xolox#70

Support for sessions with multiple TagList windows

See issue xolox#66 on GitHub:
  xolox#66

Add session_default_overwrite option (see readme for details)

See also issue xolox#62 on GitHub:
  xolox#62

Make sure vim-misc is installed, politely complain if it isn't

See issue xolox#65 on GitHub and numerous other issues before it:
  xolox#65

Bug fix: Re-implement Vim's special handling of initial, empty buffer

See issue xolox#60 on GitHub:
  xolox#60

This is a follow up to my recent changes for issue xolox#28:

  Bug fix: Disable Vim's special handling of initial, empty buffer
  xolox#28

Internal refactoring: Replace s:select_name() with xolox#session#prom…

…pt_for_name()

Internal refactoring: Merge s:get_name() and xolox#session#find_curre…

…nt_session()

Bug fix: Disable Vim's special handling of initial, empty buffer

See issue xolox#28 on GitHub:
  xolox#28

Merge pull request xolox#59: Make :RestartVim retain server name

See pull request xolox#59 on GitHub:
  xolox#59