Merge branch 'fix-candb-update-increment-bug' into 'beta'

Fix for #28: No increment in CanDB.update during creation, resulting in...

See merge request origyn/engineering/opensource/candb-projects/CanDB!25

Fix out of date simple multi-canister example to be up to date with t…

…he CanDB beta (#22)

* Fix out of date simple multi-canister example to be up to date with the CanDB beta
* bump btree to v0.3.2

Fix bug in updateAttributeMapWithKVPairs & add unit tests (#20)

Add the following unwrapping/retrieval Helper methods to Entity.mo

* getAttributeValueRBTreeValue()
* getATtributeValueRBTreeValue()

Rename all mentions of **primary** key to -> **partition** key

Change references to primaryKey to partitionKey

Update example CanDB reference to point to the main branch