Rename project from eos-parental-controls to malcontent

Rename the library from libeos-parental-controls to libmalcontent, and
the client from eos-parental-controls-client to malcontent-client.

This was done using the following mechanical edits, and no other
changes:
```
git search-replace -f EPC///MCT
git search-replace -f Epc///Mct
git search-replace -f epc///mct
git search-replace -f eos_parental_controls///malcontent
git search-replace -f eos-parental-controls///malcontent
git search-replace -f EosParentalControls///Malcontent
git search-replace -f 'eos\\-parental\\-controls///malcontent'
git search-replace -f 'Since: 0.1.0///Since: 0.2.0'
```

Note that the accounts-service extension interface has *not* been
renamed, as that would revert people’s parental controls settings in
existing deployments.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

po/meson.build

@@ -1 +1 @@
-i18n.gettext('eos-parental-controls', preset: 'glib')
+i18n.gettext('malcontent', preset: 'glib')