Updated references to new Session()

If you use new Session(), you get a 500 error, with the following message:

```log
Failed to start the session: already started by PHP.
```
Removed use command

As it is no longer needed
Added Caution note
Added extra new lines

Added new lines after 72 characters to conform with character limit standards
Fixed typo and removed extra space
fixed typo
Updated grammer issues in caution section
fixed spaces and 72 char line limit
Updated warning for Sessions
minor #3769 Updated references to new Session() (scottwarren)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes #3769).

Discussion
----------

Updated references to new Session()

If you use new Session(), you get a 500 error, with the following message:

```log
Failed to start the session: already started by PHP.
```

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | I tested 2.4.2, but it most likely will be earlier version as well
| Fixed tickets | none

Commits
-------

fa86275 Updated warning for Sessions
4e06f0e fixed spaces and 72 char line limit
3624fec Updated grammer issues in caution section
b2ac5bc fixed typo
6e6b19f Fixed typo and removed extra space
df4ef14 Added extra new lines
275dd97 Added Caution note
a64f274 Removed use command
490efdc Updated references to new Session()