core: LexoNumericComparator to comparators pkg

Moved LexoNumericComparator to the comparators package, like all the
other comparators.

Change-Id: Ic23f6efefb8f83a791cab38f3da43a78c5f885bb
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Removed comparators' Compare methods

This is probably a leftover from the C# days.
In java, comparators have a compare(T, T) method.

Change-Id: I0fa2e830a9560dc4db9929053bd7ceced48a135d
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Replace FQCNs with imports for comparators

Replaced FQCN references with imports throughout the comparators
package.

Change-Id: I80a1f040a395a5681dedd891ba5e6ddeb601ec15
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Remove comparators' empty default ctors

Removed empty implementation of the default constructor throughout the
comparators package.

These constructors have no added value, and just clatter up the code.

Change-Id: Id8477d87cd992ceba047a4f07a75337b8ed7d30d
Signed-off-by: Allon Mureinik <amureini@redhat.com>