Replace confusing checkbox with a single-entry drop-down list

This way we can at least show a message to the user when running in interactive
mode about closing any open images.

src/main/resources/scripts/Plugins/NoiSee/NoiSee_Bead_Analysis.ijm

-// @Boolean(label="NoiSee - run SNR bead analysis",description="all open images will be closed",value="true") run_macro
+// @String(label="NoiSee - Beads SNR analysis", choices={"Note: all currently open images will be closed!"}, style="listBox", description="Hit 'Cancel' otherwise!") warn_msg
 // @File(label="Beads time-series image",description="2D time-lapse acquisition of fluorescent beads") beadsimage
 // @Integer(label="Beads diameter (in pixels)",description="approximate bead diameter (in pixels)",value=15) beads_diameter
 // @Integer(label="Find Maxima noise tolerance",description="typical values: [PMT=50] [HyD (photon counting)=10] [Camera=500]",value=50) beads_noisetolerance
@@ -26,11 +26,6 @@
 //  - "roi_"  - index number of a ROI manager entry
 
 
-if (run_macro == false)
-    exit("Please select the 'run analysis' option to execute the macro!");
-
-
-
 ////////////////// function definitions ///////////////////////////////
 
 function duplicateImage(id_orig, new_name, single){

src/main/resources/scripts/Plugins/NoiSee/NoiSee_Fluorescein_Analysis.ijm

-// @Boolean(label="NoiSee - run Fluorescein SNR analysis",value="true") run_macro
+// @String(label="NoiSee - Fluorescein SNR analysis", choices={"Note: all currently open images will be closed!"}, style="listBox", description="Hit 'Cancel' otherwise!") warn_msg
 // @File(label="Dark image",description="dark field image") darkimage
 // @File(label="Fluorescein image",description="fluorescein image") fluoimage
 // @Boolean(label="Save results as PDF",description="generate a PDF with images and plots",value="true") save_pdf
@@ -19,11 +19,6 @@
 //  - "rgb_"  - image IDs of 2D RGB images
 
 
-if (run_macro == false)
-    exit("Please select the 'run analysis' option to execute the macro!");
-
-
-
 ////////////////// function definitions ///////////////////////////////
 
 function duplicateImage(id_orig, new_name, single){