Add per chart limit option

[scbizu]

impls #316

Also , closes #376

• backend storage and index cache supports per chart limit

Maybe in next release:

• lock chart to be unremovable
• provide a dry run command to clean museum(per chart) , also works with chart lock mechanism

[scbizu]

I found a problem during implementing this feature , dose all of our storage impls support the same name file covering. With the #454 , we can now update our cache index in the chart updating case , but it still can be stored into backend storage if this backend storage do not support the same name file covering or add some other more suffixes into the package name .

However, we maybe break the above case and the per-chart-limit option will also limit the same name artifact at N versions . I do not know if this should be mentioned in the next release note.

[jdolitsky]

@scbizu - where do we stand with this and #457 ?

[scbizu]

#376

[jdolitsky]

@scbizu can you rebase?

[scbizu]

done @jdolitsky