Fixed bug: Loosing separate IO ports when loading.

* description of bug
    * loading a session when SL is already running would not restore
      separate (Jack) IO ports
* analysis
    * new loops (class Looper) were added before old loops were
      destroyed
    * Jack ports are created / destroyed upon Looper creation /
      destruction time
    * hence, tried to create Jack ports that already existed (because
      they were not destroyed yet); which fails
* fix
    * loading a session is now a two phase process
    * phase 1 deletes all existing loops
    * phase 2 parses xml file and creates new loops
    * phase 2 is only started when phase 1 is done (both normal and rt
      thread completed deleting all loops)
* while loading a new session, add and remove loop commands are
  disabled (just to be on the safe side)
Fixed bug: Loosing separate IO ports when loading.

* description of bug
    * loading a session when SL is already running would not restore
      separate (Jack) IO ports
* analysis
    * new loops (class Looper) were added before old loops were
      destroyed
    * Jack ports are created / destroyed upon Looper creation /
      destruction time
    * hence, tried to create Jack ports that already existed (because
      they were not destroyed yet); which fails
* fix
    * loading a session is now a two phase process
    * phase 1 deletes all existing loops
    * phase 2 parses xml file and creates new loops
    * phase 2 is only started when phase 1 is done (both normal and rt
      thread completed deleting all loops)
* while loading a new session, add and remove loop commands are
  disabled (just to be on the safe side)
Merge branch 'fix_loosing_separate_io_ports_when_loading' of github.com:meznom/sooperlooper into fix_loosing_separate_io_ports_when_loading
Addendum to Fixed bug: Loosing separate IO ports...

* simplified load session event handling code: renamed and merged
  functions, renamed event
* entry in CHANGES file
Merge pull request #4 from meznom/fix_loosing_separate_io_ports_when_loading

Fixed bug: Loosing separate IO ports when loading.