If you want to install a new JDBC-driver you MUST start wildfly10.x.x. in STANDALONE-mode, because

YOU CAN NOT install a new module in DOMAIN-mode. Except you make it by yourself modifing the

XMl-File manually. In order to avoid typos it would be better let the CLI make install all necessary things on the system-layer, right?!

#1.

Start wildfly-server with ./standalone.sh in ~/bin

#2.

Then execute in the same Folder ./jboss-cli.sh -connect

#3.

module add --name=org.postgres --resources=/home/karl/Downloads/postgresql-9.4.1208.jre7.jar --dependencies=javax.ap,javax.transaction    

Type ENTER. Nothing will occure. If you open your Wildfly-Folder/module you will see now a new folder named org and withing the right structure and files you need later on.

Just for getting a bit more familar with wildfly-cli try to remove now the module by typing at the jboss-cli:

#-3. (only if you want be sure how it works)

module remove --name=org.postgresql

Nothing will appear on screen to tell you «succeed» or so like before. But if you have a look at ~/module the org-folder is deleted.

Next. In order to be more flexible in the future lets make more than one module with different versions of the same JDBS-Driver AND/OR you can install your needed driver (and/or versions) in the same way I do.
This might be useful if you switch to another version during production-mode smoothly just modifiying the driver within the datasource.

If you have quitted the server meanwhile repeat steps #1 and #2 like above. Afterwards type at the jboss-cli-command-line

#4. Always try to use the TAB-key for auto-insert due to convenient and correct typing.

module add --name=org.postgres941208JRE7 --resources=/path/to/postgresql-9.4.1208.jre7.jar --dependencies=javax.ap,javax.transaction

#5.

module add --name=org.postgres9941208 --resources=/path/to/postgresql-9.4.1208.jar --dependencies=javax.ap,javax.transaction

A short look in the ~/module-folder lets confirm you have now two new folders. One is named org.postgres941208JRE7 THE OTHER org.postgres9941208. OK.

Type at the jboss-cli-commandline now

#6.

quit OR \q

The JDBC-modules are already installed so you ought shutdown the wildfly-standalone-server now if you want to use the new drivers in DOMAIN-mode subsequently for declaring datasources.

But: Anytime you need to install any other new module you must use this procedure described.