Create HgStatusCommand using appropriate builder structure.

 *Change HgStatusCommand constructors call.
 *Fix for IDEA-101722
Change checking myProject for null with  if- statement to assertion.
Add annotation @Nullable for target revision argument
Add assertion if there are no branches to update or to merge with.
Refactor HgTagBranchCommand. Handle errors when load branches for action dialogs.

*Remove unnecessary usage of Consumers in HgTagBranchCommand method execution.
*Check result of command execution and handle errors.