Feat/resettable singletons

[chrisdutz]

trafficstars

Description

We are using singletons throughout the code-base. This has the disadvantage that once these are initialized, we can't re-initialize them. Especially when running IoTDB in an embedded mode, this makes it impossible to switch the storage location.

I've added "reinitializeStatics()" methods to places, were I needed to have them re-initialized.

This is actually just a hack or workaround needed till we refactor IoTDB to be a cleanly modeled fo useage of a DI framework.