Revert "Temporarily install Mallet::CrfWrapper from Linas's repository because it contains experimental fixes that should fix the Vagrant test run"

This reverts commit 4504454930879e9750e77aa0512147f9ca4cd719.
When installing Mallet::CrfWrapper, don't run unit tests because the web service test ends up as a Perl zombie process during the Vagrant test run
Change "solr_select_url" to "solr_url" in the rest of the code (default configuration, configuration example file, helper Python scripts); initial change was introduced in f12f55462917fcc32bf3707e5df6da2904aef2c9
Install 10gen's version of MongoDB in the Media Cloud's install script
Don't be brave enough to remove (obsolete) user packages but instead instruct user to do it manually and exit
Add initial ".travis.yml"
"apt-get" upgrade requires root privileges, "./install.sh" doesn't
Test if MongoDB-10gen APT source list file exists or not; add new source using privileged account
Run "apt-get update" before "apt-get upgrade" in order to fix the "Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?" error
Update all packages
Add some comments
Remove redundant commands
Use correct amount of indentation
Use travis_wait() in order to increase Travis-CI timeout from 10 minutes to 20 minutes for Perl build
Add travis_wait() to .travis.yml where it is more likely to work
Use Perl version-agnostic way of switching to Media Cloud's Perl library
On Travis-CI, don't rebuild Perl and instead use a provided version of 5.16.3
Use a more dispersed way to install Media Cloud on Travis-CI (maybe it won't timeout that way)
If Travis-CI build fails, print out cpanminus build logs to output
Don't upgrade APT's packages because it takes too much time and the test build could time out