Store pride-level configuration

[lptr]

For example the Gradle version to be used when (re)initializing the pride. Or even the default VCS.

• add a .pride/config file to the pride

• load the local configuration and merge it with the global configuration

• allow pride config to modify the global and local configurations; Git-like:

  When reading, the values are read from the system, global and repository local configuration files by default, and options --system, --global, --local and --file can be used to tell the command to read from only that location (see FILES).

  When writing, the new value is written to the repository local configuration file by default, and options --system, --global, --file can be used to tell the command to write to that location (you can say --local but that is the default).

• add pride init --purge to clear the configuration, but without this option try to load it

[lptr]

Added local config : f15dd4c

[lptr]

Won't implement --purge right now -- that switch doesn't really sound right. Let's first think about how this should work in the first place. Until then people can delete .pride/config manually.

All the rest is implemented, plus unsetting properties.