According to BIP 148 all bitcoin nodes should be comitted to signal BIP148 by August 1st. How to do this with Armory? Should we edit the shortcut for bitcoinqt as follows: -uacomment=UASF-SegWit-BIP148 as it is sugested by UASF working group? Or there is some other way for this?
Adding the uacomment does not do anything. It simply means that you intend to run a node that enforces BIP 148 in the future. It does not actually effect how BIP 148 activates nor will it mean that your node will enforce the BIP 148 rules once they activate.
To use Armory with BIP 148, just download and install the BIP 148 fork of Bitcoin Core. It will overwrite whatever Bitcoin Core install you currently have. Armory will then use that install as its local full node and will follow whatever blockchain that node is following, which, after BIP 148 activates, will be the BIP 148 chain.