Normalize global $_pm_active_polymer_styled variable

[Smolations]

In order to call out items which are brnaches in the interface, backticks are used. These backticks should be a part of the $_pm_active_polymer_styled variable value instead of being implemented each time the branch is shown.

Affected variable: $_pm_active_polymer_styled

Example:
Instead of: echo "some string with \${_pm_active_polymer_styled}` in it"`
Do this:

    export _pm_active_polymer_styled="${SOME_COLOR}\`${active_polymer}\`${X}"
    echo "some string with ${_pm_active_polymer_styled} in it"