add MetaSearch 0.2.0 (https://github.com/geopython/MetaSearch/issues/53)

cc @rduivenvoorde @kalxas @timlinux 

Initial integration of MetaSearch plugin as per https://github.com/geopython/MetaSearch/issues/53

This adds a frozen/stable MetaSearch 0.2.0 from http://plugins.qgis.org/plugins/MetaSearch/version/0.2.0/ via

```bash
cd python/plugins
lwp-download http://plugins.qgis.org/plugins/MetaSearch/version/0.2.0/download
unzip download.zip
rm -f download.zip
```
and ties it into the QGIS via `/src/app/qgspluginregistry.cpp` and `python/plugins/CMakeLists.txt`.

I also added `python/plugins/MetaSearch/CMakeLists.txt`.  Once this is firmed up, I will add this file upstream so management of MetaSearch in QGIS core is simply unzipping the stable release and adding/updating.

Things that can be improved:

- dependency management
- translation

Ideally this workflow is better managed with something like https://github.com/geopython/MetaSearch/wiki/QGIS-Core-Integration#desired-workflow-policy in the future.