fix minor bug

* FIX: error toolbar did not work properly
complete configuration category 'general'

- complete ConfigurationGeneral
- new classes for Gender and HeartRateUnit
- fix all usages of CONF_… of general values
complete configuration category 'general'
complete configuration category 'activity view'
revert changes and refactor again

* ADD: new class 'Parameter'
 - this class is for general parameter, e.g. Int, Bool, Select, …
 - this class is not connected to the database and configuration

* ADD: new class 'ConfigurationHandle'
 - this class connects a parameter and a key
 - the configuration class is now based on these handles

In addition, none of these classes holds the information for the
configuration window. Therefore another class will be needed.
complete configuration category 'privacy'
complete configuration category 'activity form'
complete configuration category 'data browser'