have telerivit send use requests instead of pycurl

pycurl is used only here and the library has some issues installing on
redhat. requests also has a much better API.
uninstall pycurl
add some properties to internal props in Domain
add mgmt cmd to make secure_submissions explicity false if not set

this is so we can change the default without the danger of changing any
current apps or domains
Use verify instead of cert
Merge pull request #2930 from dimagi/internal

add some properties to internal props in Domain
Merge pull request #2932 from dimagi/secure-submissions-migration

add mgmt cmd to make secure_submissions explicity false if not set
Merge pull request #2936 from dimagi/remove-pycurl

Remove pycurl
update submodule ref
Merge remote-tracking branch 'origin/master' into fields-to-filters