#118: implement Sphere client caching using self-autowired Spring bean

[andrii-kovalenko-ct]

Addressing #118:

Yesterday i discovered cool Spring feature (since Spring 4.3) - self autowiring for beans).

This allows to avoid those "crutches" i used for SphereClient caching factory to allow re-using calls in overloaded methods.

Review notes:

• removed SphereFactoryInternalCache "crutch"
• instead of that added self-autowired bean to the factory over @Resource annotation
• use this bean inside overloaded createSphereClient (TenantConfig) call

[andrii-kovalenko-ct]

closes #118