Updating install process

Corrected "developing" to "development" branch. Added some Ubuntu-specific instructions for installing dependencies of solr extension (php5-curl extension is needed, as well as libcurl and libcurl header files). Updated solr extension install process to use solr *stable* (more current than beta), installing via pear so it picks up php5-curl installation. Added command to add extension to php conf (needed due to change to pear install, and for Ubuntu).
I only use Ubuntu, so I'm unaware of the relevant process for RHEL, sorry.