Fix package name

[Whissi]

The previous package name "percona-toolkit" is not a valid package name for ExtUtils::MakeMaker:

$ perl Makefile.PL Checking if your kit is complete... Looks good Warning: NAME must be a package name [...]

Let us use the same package name (Percona::Toolkit) various scripts in bin/ are already using.

[hydrapolic]

Can this be merged if we rebase it?

[it-percona]

All committers have signed the CLA.

[Whissi]

Rebased, CLA should be signed.