PROTON-445: Python install now honors CMAKE_INSTALL_PREFIX

The language bindings will now honor this prefix, both the default value
and a user-specified value.

Developers can override it, though, by specifying PYTHON_INSTALL_PREFIX
at the command line as well. This will allow for installing the Python
bindings to a different directory if so desired.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1547577 13f79535-47bb-0310-9956-ffa450edef68
PROTON-445: Perl install now honors CMAKE_INSTALL_PREFIX

The language bindings will now honor this prefix, both the default
value and a user-specified value.

Developers can override it, though, by specifying PERL_INSTALL_PREFIX
at the command line as well. This will allow for installing the Perl
bindings to a different directory if so desired.

Also updated the installation pieces in CMake to simplify it.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1547578 13f79535-47bb-0310-9956-ffa450edef68
PROTON-464: Install Ruby bindings to install prefix if specified.

If the user provides a CMAKE_INSTALL_PREFIX on the command line, then
that directory is used to install the Ruby language bindings. If no
install prefix is specified then the Ruby bindings honor the directory
specified by the Ruby VM itself.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1547579 13f79535-47bb-0310-9956-ffa450edef68
PROTON-445: PHP install now honors the install prefix.

If the install prefix is not "/usr" then the INI directory is placed
below it. This is to accomodate a system install as opposed to a
developer install.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1547597 13f79535-47bb-0310-9956-ffa450edef68