Show file parameters as mandatory in swift-*-info man pages

Changes the file parameters on command line to use the convention of
<file> for a mandatory option rather than [file] which suggests an
optional flag. Also drop to lower case as is convention in other man
pages.

Change-Id: Icfb4b4786343eb493a73b092cad1fdadc935d066

doc/manpages/swift-account-info.1

@@ -24,7 +24,7 @@
 .SH SYNOPSIS
 .LP
 .B swift-account-info
-[ACCOUNT_DB_FILE] [options]
+<account_db_file> [options]
 
 .SH DESCRIPTION
 .PP

doc/manpages/swift-container-info.1

@@ -25,7 +25,7 @@
 .SH SYNOPSIS
 .LP
 .B swift-container-info
-[CONTAINER_DB_FILE] [options]
+<container_db_file> [options]
 
 .SH DESCRIPTION
 .PP

doc/manpages/swift-object-info.1

@@ -25,7 +25,7 @@
 .SH SYNOPSIS
 .LP
 .B swift-object-info
-[OBJECT_FILE] [options]
+<object_file> [options]
 
 .SH DESCRIPTION
 .PP