etnservice has an undocumented dependency on etn

[PietrH]

Lines like:

etnservice/R/get_acoustic_receivers.R

Line 69 in b013e6e

readr::read_file(system.file("sql", "receiver.sql", package = "etn")),

Call an sql file installed in etn

This is causing calls to etnservice to fail when a version of etn is installed that does not have these files.

While etn can be dependent on etnservice, etnservice should not be dependent on etn.

• Fork sql files from etn to etnservice #46
• remove dependency on etn in sql file calls #47