Improve discussion around using store versus executestore

From a user:

Another thing I have seen is using set and exeuteset method usage. When in samples we are using set, it is not very clear that it might fail due to memory limitation and instead of using set we should use executeset and lookout for result and if it is fail due to memory issue than we should try again in few millisecond so couchbase do memory clean-up in mean time for new data.