Fix for 'Remove All entries from this domain' on history item

[fnkkio]

Fixes #1604

[Emdek]

I'm not sure what should be the proper approach here, one thing is for sure, QRegExp shouldn't be used in new code and it is not needed here at all.
www. is just an optional subdomain, perhaps we should match all subdomains? Or maybe split it into two actions...
Could you please check how similar features behave elsewhere in such cases?

[fnkkio]

I revised my previous commit and came up with a better solution.

[fnkkio]

'+1' at the end because:

• in case lastIndexOf does not find a dot, it will return -1, adding 1 will set the domainStartIdx to 0
• in case lastIndexOf does find a dot, it should return the idx after the dot

ie.
220.ro -> lastIndexOf returns -1, we add 1, domainStartIdx = 0, return value = 220.ro
vid.220.ro -> lastIndexOf returns 3, we add 1, domainStartIdx = 4, return value = 220.ro

[fnkkio]

@Emdek Do you think this is the right approach ? (In the latest version of this PR I am removing history items for the domain and all its subdomains)