Subcorpus, simple mode interface tweaks

• select by list button: add the valid separators to the dialog box
• add reverse button: reverse the selection

changed milestone to %TXM 0.8.4

added tool::subcorpus ui labels

added status::to validate label

duplicate of #3325 (closed)

closed

removed status::à tester label

added status::rejected label

removed status::rejected label

added status::rejected label