rename module to lowercase

src/nf_modules/urqt/trimming_single.nf

src/singularity_modules/bedtools/2.25.0/BEDtools.def

src/singularity_modules/bedtools/2.25.0/build.sh

src/singularity_modules/bowtie/1.2.2/Bowtie.def

src/singularity_modules/bowtie/1.2.2/build.sh

src/singularity_modules/bowtie2/2.3.4.1/Bowtie2.def

src/singularity_modules/bowtie2/2.3.4.1/build.sh

src/singularity_modules/bwa/0.7.17/BWA.def

src/singularity_modules/bwa/0.7.17/build.sh