MQI client: Client configuration stanzas moved into a new configuration file

Client configuration information is moved from existing configuration stanzas into a new configuration file, mqclient.ini.

Moving client configuration information affects existing settings; for example:

Set the TCP KeepAlive attribute for client connections in mqclient.ini ; for example:
```
TCP:
KeepAlive = Yes
```
An existing setting in qm.ini is ignored.
Set ClientExitPath in mqclient.ini ; for example:
```
ClientExitPath:
ExitsDefaultPath=/var/mqm/exits
ExitsDefaultPath64=/var/mqm/exits64
```
An existing setting in mqs.ini is moved to the client configuration file when you upgrade the client. If you add values to mqs.ini, they are ignored.
Set JavaExitsClasspath in mqclient.ini.
Do not continue to use the Java system property com.ibm.mq.exitClasspath. Existing settings continue to work, but they are deprecated. The setting in mqclient.ini has precedence over the Java system property.