Fix spelling mistakes in comments and descriptions

Thanks, codespell!

plugins/power/currentcost

@@ -58,7 +58,7 @@ The configuration can be broken down into the following subsections:
 
 =item env.device
 
-Specfies the device node where the CurrentCost monitor can be found. You may find it useful to use a udev rule to symlink this somewhere permanent.
+Specifies the device node where the CurrentCost monitor can be found. You may find it useful to use a udev rule to symlink this somewhere permanent.
 
 =item env.baud
 
@@ -100,7 +100,7 @@ The time period for which C<env.nightrate> applies. This should be of the form C
 
 =item env.standingcharge
 
-The standing charge in hundreths of a C<env.currency> per month. If you do not have a standing charge, set this to 0.
+The standing charge in hundredths of a C<env.currency> per month. If you do not have a standing charge, set this to 0.
 
 =item env.metertype
 

plugins/power/nutups2_

@@ -239,7 +239,7 @@ sub common_config {
 		print $id . ".label " . $field . "\n";
 		print $id . ".type GAUGE\n";
 
-		# Draw nominal values a litle thinner
+		# Draw nominal values a little thinner
 		print $id . ".draw LINE1\n" if $nominal;
 
 		print_range_warning($id, $key, $values);

plugins/power/upsmonpro_

@@ -121,7 +121,7 @@ END
 sub run_config_load {
   print <<'END';
 graph_title UPS Battery Load/Capacity
-graph_vlabel precent%
+graph_vlabel percent (%)
 graph_scale no
 graph_category sensors
 battery_load.label battery_load