file() and wildcard-file() sources (#202)

Changes:

- Removed "DEPRECATED" titles from file() source 
- Added new platform statement for file() source that warns the user and
suggests the use of wildcard-file()
- Removed options subsection from file() source, users are directed to
wildcard-file() options as an alternative
- Made the note to alert the users that base-dir() and
filename-pattern() are not functional with file() source only
wildcard-file()

Author: zsoltgyulai94

_includes/doc/admin-guide/notes/wildcard-option-warning.md

@@ -0,0 +1,3 @@
+**NOTE:** 
+This option is only available for the `wildcard-file()` source but unavailable for the `file()` source.
+{: .notice--info}

doc/_admin-guide/060_Sources/020_File/000_File_source_options.md

@@ -1,10 +1,10 @@
 ---
-title: 'file: Collecting messages from text files (DEPRECATED)'
-short_title: file (DEPRECATED)
+title: 'file: Collecting messages from text files'
+short_title: file
 id: adm-src-file
 description: >-
-    The file() source has been deprecated. For a more stable performance, use the [[wildcard-file() source|adm-src-wild]] instead. Collects log messages from plain-text files, for example, from the logfiles of
-    an Apache webserver. If you want to use wildcards in the filename, use the [[wildcard-file() source|adm-src-wild]].
+    Collects log messages from plain-text files, for example, from the logfiles of
+    an Apache webserver. If you want to use wildcards in the filename, use the [[wildcard-file() source|adm-src-wild]]. Currently, {{ site.product.short_name }} supports the file() source to maintain certain compatibilities, but it is advised to use the wildcard-file() source for longevity reasons and more configuration options.
 ---
 
 The {{ site.product.short_name }} application notices if a file is renamed or replaced with
@@ -49,3 +49,5 @@ treats messages received from files as sent by the kern facility. Use
 the **default-facility()** and **default-priority()** options in the
 source definition to assign a different facility if needed.
 {: .notice--info}
+
+For the configuration options available in the `file()` source, see wildcard-file() source options.

doc/_admin-guide/060_Sources/020_File/002_Notes_on_reading_kernel_messages.md renamed to doc/_admin-guide/060_Sources/020_File/000_Notes_on_reading_kernel_messages.md

@@ -10,6 +10,8 @@ The wildcard-file() driver has the following options:
 
 ## base-dir()
 
+{% include doc/admin-guide/notes/wildcard-option-warning.md %}
+
 |Type:|      path without filename|
 |Default:||
 
@@ -39,6 +41,8 @@ source s_files {
 
 ## filename-pattern()
 
+{% include doc/admin-guide/notes/wildcard-option-warning.md %}
+
 |Type:|filename without path|
 |Default:||