2.6.0
* The plugin is aligned with OQ-Engine version 2.6
* Added a warning message in case of connection with a potentially incompatible
version of the OQ-Engine Server
* The list of calculations displays the Calculation Mode instead of the Job
Type
* Loaders for OQ-Engine hazard outputs can read the new format introduced in
OQ-Engine version 2.6
* Layers for hazard curves are stored in a more convenient way, keeping a scalar
value per cell instead of a json string
* Integration tests check that all implemented loaders for OQ-Engine outputs are
tested at least once
* Both workflows aggregating loss points by zone are tested on Travis (1: using
SAGA; 2: using the fallback algorithm)
