Never downgrade packages on upgrade

This is related to #985
solver: Check if a package is available before trying to upgrade at least this version

if that's not the case, we just fall back to the previous behavior. In practice, this should not happen to often ...
Added a shell-script that makes release build/upload easier
Update the opam_installer script to use the new releases
Merge pull request #1107 from AltGr/easier-release

Added a shell-script that makes release build/upload easier
opam_installer.sh: download temp files in /tmp
Update release instructions
Merge pull request #1109 from samoht/master

Never downgrade packages on upgrade
Merge pull request #1112 from AltGr/easier-release-2

improve opam_installer.sh, update release instructions
Document environment variables in their own section
Closes #1066
Attempt `-p` parameters to the `patch` command until 5
Fixes #113
Improve some error messages with malformed files
(much more useful when you are given the incriminated file name)
Backported improved sanitization/quoting when calling external solver from dose.
Do not use which when trying to locale aspcud.
Merge pull request #1124 from vbmithr/nowhich

Do not use which when trying to locale aspcud.
Merge pull request #1115 from AltGr/man-env-vars

Document environment variables in their own section
Merge pull request #1117 from AltGr/patch-level-try-again

Attempt `-p` parameters to the `patch` command until 5
Merge pull request #1118 from AltGr/improve-file-errmsg

Improve some error messages with malformed files
Turning the 'NOTE: blah exists although blah is not installed' into debug
Closes #1111
overriding archive files from the package is not really a warning