Use old/new taks depending on whether jarsign.storepassfile is set

Restore old signjar/genkey tasks for Java<1.7
Use the new exec invocation with -storepass:file only if property jarsign.storepassfile is explcitly set
Revert "Replace jarsign.storepass property with jarsign.storepassfile"

This reverts commit 94b0f13505aee0e061d374a65b1b63d55da4e0b2.
Add commented out note about jarsign.storepassfile
Add tsaurl to old signjar tasks
Move jarsign into a new macrodef, echo jar name when signing