use status-react-jenkins as CI library

This PR extracts all the ci/*.groovy scripts into a separate private repo located at:
https://github.com/status-im/status-react-jenkins

The main reasons for a separate repo are:

* Hiding the internal details of our CI setup
* Hiding names of Jenkins credentials available in CI jobs
* Lowering attack surface for malicious external contributors
* Increasing focus on PRs related to CI setup

You can read more about how Jenkins pipeline shared libraries work here:
https://jenkins.io/doc/book/pipeline/shared-libraries/

In simple terms I've added the repo to the main Jenkins configuration in "Global Pipeline Libraries" section and load it using:

  library 'status-react-jenkins@master'

Which makes globally available all of the libraries defined in the `vars` directory of that repo.
This also eliminates the need for statements like `android = load 'ci/android.groovy'`.

Signed-off-by: Jakub Sokołowski <jakub@status.im>

scripts/generate-keystore.sh

@@ -22,7 +22,7 @@ if [[ -z ${KEYSTORE_PATH} ]]; then
     KEYSTORE_PATH=$(property_gradle 'KEYSTORE_FILE')
 fi
 # Replace ~ with proper absolute path
-KEYSTORE_PATH=${KEYSTORE_FILE/#\~/$HOME}
+KEYSTORE_PATH=${KEYSTORE_PATH/#\~/$HOME}
 
 if [[ -e "${KEYSTORE_PATH}" ]]; then
     echo -e "${YLW}Keystore file already exists:${RST} ${KEYSTORE_PATH}" > /dev/stderr