better visability of peak charts

utilities/errortexts.js
   - typos corrected

sensorspecials/noise.js
   - accept only values for span lower than default values

sensorspecials/noiseChart.js
   - add zIndex to options

utilities/errortexts.js

@@ -10,7 +10,7 @@ export const NOPROPSREAD = `No properties read for sensor ${'xx'}`
 export const NOPARAMETER = 'No parameter given'
 export const RESPSTATUS = `Returned status = ${'xx'}`
 export const NODATA = 'No data found'
-export const SYNTAXURL = 'Syntax error in calling url'
+export const SYNTAXURL = 'Syntax error in calling url!'
 export const WRONGTYPE = `Sensor ${'xx'} is not of type ${'yy'}`
 export const NOLASTDATES = `Problems fetching last dates from database`
 export const NOPROPSFOUND = `Properties collection not found`