pager: remove pager code from core

pager: further simplify code, clean up comments

Use the pager given by the environment to display long output Unix systems usually have a PAGER environment variable set. If it is set, mercurial will use the pager application to display output. Two configuration variables are available to influence the behaviour of the pager: pager.application sets the application to be used pager.quiet silences Broken Pipe errors that might occur when the user quits the pager before mercurial finished to write the output

hgk: don't exit if mercurial commands only print warnings

tag: allow multiple tags to be added or removed - Example: "hg tag -r 42 build-25 beta-1" will add tags build-25 and beta-1 for rev 42. - The deprecated and undocumented usage "hg tag arg1 arg2" used to emit a warning, then add tag arg1 for rev arg2 (equivalent to "hg tag -r arg2 arg1"). It will now add tags arg1 and arg2 for the current revision. - If one tag triggers an error, no tags are added/removed (all or nothing).

tests: update test-command-template for the new {isodatesec} filter

Add an {isodatesec} template, to show seconds too.

convert: Add convert.cvsps option to set up an alternate cvsps command line.

hgwebdir: Tiny fix for webdir on non-symlink capable platforms.

Add tests for cloning from a all-history bundle