Show private key state & allow healing

[episource]

The following changes are introduced:

• The "Edit Encrypted Key File" Dialog also shows private key connections state (optionally use this as early indicator, whether there might be a incompatibility)
• add private key state "mismatch" (in addition to "connected", "not connected") - "mismatch" is shown if querying the private key fails with either NTE_BAD_PUBLIC_KEY or NTE_BAD_KEY. Both are likely related to corruption/misconfiguration of the system's certificate store.
• allow healing when querying private key properties (disable CRYPT_ACQUIRE_NO_HEALING option) - healing will sometimes solve NTE_BAD_PUBLIC_KEY issues*
• also pulls in the changes of Optionally filter key usage in frontend #14

*) On my systems I needed to fiddle with the CERT_KEY_PROV_INFO_PROP_ID provider property associated with a cert to force NTE_BAD_PUBLIC_KEY: I've overwritten this with the value of another certificate (for another key slot, but sharing the same algorithm parameters). Enabling healing worked around this forced NTE_BAD_PUBLIC_KEY. I'm not aware of negative side effects that might come along with the healing, other that it might change persistent provider data.

I could imagine, that NTE_BAD_PUBLIC_KEY might also occur, when the key on the smartcard is recreated / overwritten without updating the computer's or key file's cached certificate. Was not able to easily reproduce this though (e.g. overwriting a yubikey PIV slot led to "not connected" / NTE_BAD_KEYSET during my testing).