When the YACY_DATA_PATH environment variable is set, shell scripts will
now use the given path instead of relative ../DATA which remains the
default when the variable is not set.
Necessary in the context of Snap package (see issue #254) as YaCy is
started with startYACY.sh and an absolute DATA parent path in parameter.
Because curl and wget do not let use a hashed password as parameter,
YaCy shell scripts which require authentication are now interactive by
default when HTTP Digest is the only available authentication method.
Batch mode can still be available trough the use of an environment
variable : YACY_ADMIN_PASSWORD.
Other improvements :
- added backward compatibility for Basic Authentication
- fixed curl/wget presence detection
- do not return with exit code 0 when an API call failed, and print an
error message when the case occurs
- documented available authentication options for API calls
