First round of changes to migrate pager inside fish, in preparation for
presenting completions underneath.
More work on builtin pager
Merge branch 'master' into pager
Migrating new pager implementation into a class. Further work on
constructing a screen_data_t from it.
Merge branch 'master' into pager
Teach screen how to render completion page. Correct spacing in
completion page contents.
Merge branch 'master' into pager
Merge branch 'master' into pager

Conflicts:
	screen.h
Update pager colors to use new non-bitmask architecture.
Merge branch 'master' into pager

Conflicts:
	highlight.h
Clean up pager on exit from interactive read
Merge branch 'master' into pager
Initial support for navigating completions that appear under the
commandline using arrow keys
Implement and document new -P / --paging-mode flags to commandline, to support new
pager
Merge branch 'master' into pager
Further work on keyboard navigating the completion list
Improved navigation of pager list. Added tests for it too.
Support for correctly resizing pager contents.
Correctly clear pager contents on ctrl-C
Support for scrolling through the pager