[log] Disable VcsLogJoinerTest until date-order is supported
[log] create SimpleHash & SimpleCommit for tests to run w/o platform

We could make graph tests to be UsefulTests instead,
but it seems to be harder, and will slow down the tests.
[log] Let GraphBuilder tests skip check leaf nodes for references

Let GraphBuilder descendants override createBranch() without
reference check and root search procedure.
Use ExtendsListFix instead of custom "Make class 'Serializable'" quick fix
Use ExtendsListFix instead of custom "Make class 'Cloneable'" quick fix
[log] revert accidental commit
use the proper API in rename (IDEA-113698 Getter code generation removing "is" from getter method name)
register "Missing 'package-info.java'" inspection