Merge pull request #12 from ktlim/ktlim/doc-fix

Fix eupspkg.py doc
Makefile: remove write permission on directories with python

Merely making the files read-only wasn't sufficient to stop
saving recompiles.
Makefile: more careful to remove directory write permission

Also restore write permission before re-installing.
Makefile: fix cut/paste
Specifying a command line VRO disables automatically adding tags (as both VRO and tags are not permitted)
Added "eups tags --clone OLD NEW" and "eups tags --delete XXX"
Attempting to clone invalid tags shouldn't be a fatal error
Fix handling of --keep with tag/vro specifications in table files
Add syntax-colouring (and comments) while editing table files in emacs
Interpret non-absolute paths relative to $PRODUCT_DIR in -r statements in table files
Added ability to push verbosity onto the stack

Also added verboseUnsetup, which is used internally by unsetupRequired
(see next changeset)
Implemented unsetup{Required,Optional}

Useful in top-level table files, e.g. my classic "work" package, where you
want to tune exactly what products appear in the setup environment.
x = v1 if l else v2 is not available in python 2.4  (githug #14)

Also reworded some comments so that a search for " else " is useful
Support e.g. eups declare -t XXX -r DDD PROD VERSION

In general, if we are changing a definition and also declaring a tag,
generate a tag:XXX version with the changed attributes
Make "eups unsetup" cleanup all eups shell variables
Ignore "-t newest" tags in ~/.eups unless that's the only version available
Added "version!" to the vro; like "version" except doesn't disable --keep

Motivation:  it's useful to set an absolute version even when you want
to keep already setup products.  The absolute path specification is also useful,
so here's a way to support the latter.  E.g.
   setupRequired(hscPipe --vro version 2.10.0b_hsc)
   setupRequired(astrometry_net_data --vro version! sdss-dr8)
Renamed "newest" tag to "latest".

Maybe it's just an Real English thing, but "newest" just sounds wrong.
It's clearer if we complain about an obvious filename
Documented if statements in table files